Urea-formaldehyde polymers of high agronomic value



Oct. 11, 1960 J. P. KEALY 2,955,930

UREA-FORMALDEHYDE POLYMERS OF' HIGH AGRONOMIC VALUE Filed Oct. 19, 1956 s s s s ssn q I 1 w; u] Q l a N o f f .li /l "E INVENTOR.

BY JOSPIQ R Keaig/ TTORNEY United States Patenrff-() UREA-FORMALDEHYDE POLYMERS OFTHIG AGRON OMIC VALUE .Joseph P. Kealy,'Lansing,'Ill., 'assigner to Swift & Company, Chicago, Ill., a corporation of Illinois NoDrawing. .Filed Oct. 19, 1956,'Ser. 1510.617314' .10 Claims. 4(Cl. '7l-29) The present applicationwhich is'a Acontinuationin-part of application 4for Urea-formaldehyde Polymers of High Agronomic Value, Serial No. 555,786, ledvDecem'ber 28,

1955, now abandoned, relates in general to the preparation of fertilizermaterials containing urea-formaldehyde condensation products. More particularly, the invention relates to aprocess-for condensingrurea and Vformaldehyde together'in the 'presence of phosphatic fertilizer substrate,

inenting the nitrogen content of fertilizerlmixtures. For

example anhydrous ammonia, aqua ammonia land 'arnmoniacal solutions of urea or ammonium 4nitrate may be tused to treat acidicsuperphosphates `whereby Ito `substantially increase their nitrogen fcontent. 'Salts lcontaining nitrogen in an available form are-also used inthe preparation of mixed fertilizers. Such salts are ammonium kvnitrate, sodium nitrate, .ammonium sulphate land the like. Another source of available nitrogen which lhas become particularly :popular recently fis the Vclass 7of compounds known as ureaeformaldehyde condensation products. These condensation products `are resinous in natureand are suitable as rnitrogen sources since they contain nitrogen in a .water-insolubleform which is not leechedoutinlthe soil .immediately Vfollowing application to growing plants. They are particularly suitable for use in fertilizers 'since, as pointed out in the copending application of E. N. Mortenson and l. P. Kealy, Serial No. 530,416, filed August 24, '.1955, nowabandoned, entitled "fNoniBurning Plant Food, ureasformaldehyde condensation products, unlike -many chemical sources of nitrogen, show virtually 'no .tendency .to burn plant leaves '.throug'h zplasmolysis. "llasmolysis is lencountered whenever most `o'ftheunore .commonly used ferilizersalts are :applied to 'plant leaves and effects a burn ,or discoloration and a Ldebilit'a'tion-fof thezplants.

In general the accepted procedure has'been `tofirstcondense lthe urea and formaldehyde :infan .aqueousfsolution in thefashion detailed LbyxClark, Yeesand .Loveiin :lnd.!& Eng. Chem., vol. 40, Apage ,1,178 (1948) 'and 'thereafter admix the resin with any additional fertilizer 'solids irequired, such as superphosphates (usually ammoniated), potassium nitrate,ammonium nitrate, etc.

However, the urea-formaldehyde'condensation products are more conveniently'formed .in situ.attheftirne oflthe ammoniation of superphosphates. Theureasandformaldehyde Vare Y charged into fthe mixing chamber containing the superphosphateandbecausef .theh'eatwvhich fis Ygiven .oft 4in the exothermic neutralization trreacton, :the econ'- densation of urea lwith.formaldehyde is initiated. Also, Vthe condensation products mayV be produced `in :situ in the presence of vstraight unammoniatedsuperph'o'sphates. Such an approach is suggested -in the/Davenport Patent No. 2,618,546. f

Most of the urea-formaldehyde condensation-.products which :have been .made in the Vpast howeverahave one l-possible,rgiven proper temperature control.

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f2 rather yobjectionable feature. They ycontain `nitrogen in such a formthat it is not suihciently available foriuse tby .thelgrowingfplant 'To be ofranywalue .to the plant, .the nitrogen mustbe in such aiform that it'is susceptibleito attack'by thesoil bacteria that normally convertsl organic and ammoniacalforms of nitrogen to the readily available 'nitrate form which Ais easilyassirnilated bylplants .during the course of the growing'season. Workers infthefield have attempted to zrely upon the Clark et al. :report -mentioned'earlier and becauseofthis.havefailed .to properly condense the urea .and formaldehyde when Yprepai-ingzthe -resin"in situ in the presencerof. fertilizer .phosphati'crnaterial-in part because ofthe strong butfering eiect o''zthe 'acidic phosphatic milieu on .therelatively small Jquantity vof urea-formaldehyde material.

lt `istherefore Vanobject `of this invention to providera method-for Athe manufacture of urea-formaldehyde .condensation .products .in situ .in the lpresence iof acidic -phosphatic'substrates which, while exhibiting the .customary desirable properties Aassociated with such resinsgare further capable of supplying substantial Vamounts ofavailable Water-insoluble nitrogen.

It iisl .a further object :of this .invention to Vprovide a Ymethod for theminlsitu `manufacture of urea-formaldezhyide'condensation products of high agronomie valnexin the vpresence of .superphosphates, the-'agronomie value tbeingdesignatedin iterms ofa high availabilityindexfand -ahigh lpercentage lof urea 4nitrogen condensed to .waterinsoluble nitrogen. i

.Anotherbject ofithis inventionzis to A.provide a method :for substantially .increasing .the :value of .urea-formaldehyde condensation products as sourcesfofslowly'available snitrogen. i

Further objects 'and advantages of vthis invention, not

-specicallyeset forth,xwill vbecome apparent toene/skilled iin .theduring .the course of the description'which follows.

`. vBroadly, :acidicisubstrates in the presence ofiwhichfit is ydesirable to form'urea-foriinaldehyde condensation prod- .uctszinaccordance with thisinvention are ordinary superphosphates, smono, vdi iand tri basic,.meta phosphate and other .mono andV di phosphates. The formation of urea v'formaldehyde condensation products in' situ lin these 'materials `has not been Aconsidered:commercially feasible 'partially because the pH of the phosphate materialis ltoo low, about 2.5 for supers, for example, and extreme of low temperatures are required -in order to l*obtain a condensed lmaterial 'with the proper amount of .available nitrogen. rBut this approach may nevertheless be used :since 'superphosphates may ,be ammoniated to `incorporate nitrogen ingredients in the product and during such ammoniation .the pH of the product is raised to the extent that .it is'practical to form therein urea-formaldehyde lcondensation .productsprovided the temperature is carefully controlled, as will be detailed thereafter. 4Instead of ammoniating :the phosphate,'it is also possible to adjustthe pH'by other vmeans, such as'the addition of other-a kalinermaterials,ito

a point where rin .situ urea-formaldehyde condensation lis Ordinarily, however, in the manufactureofmixed goods :in accordance with this invention, solid superphosphate,'mono,idi or tri-basic, 'or other phosphate material Yis ammoniated toin- Acorporate the maximum amount of fixed znitrogen. The urea, either asa liquidor in solid form, may be introduced before lor .during ammoniation A tsolution Vcontaining formaldehyde is 'then added and the solute condenses with the-urea. Itisthen ordinarily necessaryto cool .the .product before vfinal storage -in a plant pile. The cooling Vis necessary to obtain a condensation product-of suiiicient agronomie value. It `is `also possible, though not preferred, totemploy this'V process without subsequently Vcooling,:but if lthegproduct obtained is to have the` desired `a. form (adequately condensed) that the nitrogen Yavailable over a long period of time.

Vagronomie activity, various conditions must prevail dur- 4The pH of the mixture, the ratio of urea to formaldehyde,

and the temperature of curing must be carefully correi i -i 9,955,930/

`lated since all play a part in determining whetherV the product will have a high availability index and be in such is slowly By means of the teachings of this invention, it is pos- -sible to securel an in situ formedurca-formaldehyde condensation product in admixture with a phosphatic sub- -strate in which `an appreciable part of the urea nitrogen,

preferably 50% or more, is condensed to the desired Awater-insoluble form and in which the nitrogen availability index (A.I.) as defined by the methods published and page 16, paragraphs 237 and 238, is at least 40 percent. A minimum availability index of 40 in ureaformaldehyde polymers has been determined by the Association of VAmerican Fertilizer Control Officials to be necessary for the polymer to release nitrogen quickly enough to be of agronomie value. This is reported in OcialV Publication #6 A.A.F.C.O., November 1954, paragraph No. 16, page 14. Aswill be more-specifically pointed out below, with proper selection or correlation vof the urea Vto formaldehyde ratio (between 1.0 and 2-.75

` will be avoided. The availability index of the condensed nitrogen will be found to be at leastabout 40 and, in

inthe 195s ed.' oniciai Methods of Analysis, Association i /of Ocial Agricultural Chemists, page 14, paragraph 232 4 Where too low a pH, one below about 3.0 is used, the nitrogen is too well bound up and diiicult of decomposition to satisfy the needs of most plants. Thus, control of the pH enables the production of a product which supplies nitrogen in a form such that it`is easily converted to water-insoluble nitrogen and is knot rapidly dissipated in the soil. At the same time pH control allows the formation of ,a product which is not so greatly condensed that it resembles the"solid resin used in making solid plastic articles. Control of the pH also enables theV binding up of virtually all` ofthe urea in such manner that it is not allowed to pass directly into the soil. ln order to secure the desired resultsV where the pH and temperatureVY of cure are carefully regulated, the ratio of urea-to-formaldehyde may be varied anywhere between about 1.0 and 2.75 to 1. The term formaldehyde as used herein includes any of its forms, such as the gaseous and aqueousl solutions of any concentration. Paraformaldehyde may also be used if sutlcient water is added to initiate the reaction.

Also suitable as a source of formaldehyde is a commer- Ya formaldehydesource since it contains an excess of the preferred embodiment of the invention, the percentage I urea nitrogen condensed to water-insoluble nitrogen will be at least 50.

Y The single ligure of the accompanying drawings graphically represents the interrelationship of the pH prevailing at the time of contact ofthe urea and formaldehyde, the

urea to formaldehyde mol ratio and the temperature dury ing the curing operation which must be maintained if .one is to carry out the process andV obtain the product of this invention. The graph will be discussed more in detail hereinafter.

More particularly, the temperature of the phosp'hatic- I uct which is at least 40 A.l. and in whichat least 50% of the urea nitrogen is condensed to water-insoluble nitrogen. The relatively high temperature ordinarily obtained formaldehyde over urea where the relationship of one ingredient to the other in the finished product is almost always reversed, the urea being present in excess or at least in molar quantities equal to those of formaldehyde. Where this solution is used, the condensation has already proceeded to the extent of causing the formation of monomethylol urea. It is only necessary to supply proper quantities of additional urea under appropriate conditions of pH and cure temperature to obtain the properly condensed fertilizer ingredient. Another suitable source of formaldehyde is hexamethylene tetramine, 6 mols of formaldehyde combined with l0 mols of ammonia. This material breaks down in moist acidic environments, behaving thereafter like a solution of formaldehyde. |Irrespective of which formaldehyde source is selected, it is essential that the urea quantity be raised to the proper molar ratio, as determined by the graph, only when the conditions of pH and cure temperature are properly under control. Under'condensation, as with the above referred to solution, f can always be corrected but overcondensation becomes possible as the urea quantity is increased and can only be avoided if the various conditions are carefully controlled.

The urea is preferably irst mixed with any of those solid fertilizerV ingredients ordinarily employed in the preparation of mixed goods containing phosphatic material. -These fertilizer ingredients to which the urea is added may include superphosphates themselves, salts of potassium, hydrated lime, dolomite, coloring matter, etc.

at the time of the initial condensation of urea and forml Y.perature usually less than 160 and as low as about 75 F; is preferably obtained shortly thereafter to avoid over condensation. The pH at the time of the condensation reaction. is important because at a pH above 6.5 too much of the condensation product is water-soluble.

'While the nitrogen in this Water-soluble material nitrilies slightly slower than that in mostv inorganic nitrogen ,h -sources,'itA is'not as effective anddesirable as nitrogen in a properly condensed urea-formaldehyde product.

Theaddition of the formaldehyde may conveniently take place at the time of the introduction of the other liquid ingredients, such as liquid anhydrous ammonia or B- .liquor (an approximately 30 percent solution of ammonia or commercial water solutions of ammonium nitrate and/or urea).A The free ammonia performs two functions simultaneously when added to a superphosphate.' It reacts with the free phosphoric acid and the monocalcium phosphate of the superphosphate, converting the former to monoand di-ammonium 'phosphate and the latter to monoand di-ammonium phosphate and dlcalciur'n phosphate. Similar reactions occur when other phosphatic material is substitutedY for superphosphate. Also,'suicient heat is developed by these reactions to initiate the urea-formaldehyde condensation. Temperatures in the vicinity of F. or higher are commonly encountered. The product obtained maybe used either in a conventional type fertilizer (which may burn turf due to itsplasmolysis eect) or it may be incorporated in a non-burning fertilizer of a type described inthe aforementioned copending application. Where a burning type 0f product is satisfactory, ammonia alone may be sufli- ,cient to yadjust the pH to the proper level. However, where a product is desired -which exhibits non-burning characteristics and, as discussed in detail in the aforementioned copending application where, therefore, lthe ammoniation is terminatedat thepointatwhich only the stoichiometric amount of ammonia to convert the free acid and monocalcium phosphate to monoammonium phosphate and dicalcium phosphate is present Y(see Manual on Fertilizer Manufacture, 2nd edit. pagea45, Vincent Sauchelli), the pH prevailing in the mixture of the urea adn formaldehyde ismuch too low for the pro- `duction of a good urea-formaldehyde product. The ureaformaldehyde condensation productV obtained under these conditions is over condensed and contains small amounts of available water-insoluble nitrogen and excessive amounts of unavailable nitrogen.

As a solution to the problem outlined above, it has been found that by the Vuse of another Vnon-amrr^.oniacal basic material, such as calcium hydroxide (hydrated lime), calcined dolomite or magnesium oxide or-other base, the pH may be adjusted upwardly so that a condensation product may be secured lwith better agronomie value than that obtained at lower pH levels. Table l below indicates the results of carefully controlling the pH of a standard superphosphate-containing fertilizer mix by the use of calcium hydroxide during the period of time the formaldehyde and urea are initially condensing one with the other in the presence of superphosphates undergoing ammoniation. All percentage figures given in the table were based upon the total weight of the mix under consideration, the pH is that prevailing in the mix several minutes after the condensation reaction and A1. refers to the availability index of the nitrogen .bound upY :in the U/l;` product after a two-week cure.

1 Vfater insoluble nitrogen. 2 Hot water insoluble nitrogen.

These urea-formaldehyde products were used to supply 4.88 units of nitrogen; a unit of plant food as de- Aned in the Official and Tentative Methods of Analysis, page 901, 6th edit., 1945, published by the Association of Oicial Agricultural Chemists (AOAC) is pounds of plant food or 1% of a ton. It may easily be seen .that as the pH is raised by increasing the amount of calcium hydroxide the A.I. increases. Thus, itis possible to reduce the amount of ammonia present (see column labeled Percent Ammonia Nitrogen (percent NHsH), Formulae 4 and 5). This reduction of NH3 may be compensated for by increasing the pH through the addition of a second base. Note that all formulations subsequent to l have satisfactory Al values. For a detailed discussion of the significance of the termavaila bility index and its relation to the standard nitriiication test of the Association of Oiicial Agricultural `Chemists, see the articles entitled Chemical Method For Available Fertilizer Nitrogen in Urea-Formaldehyde, by W. A. Morgan and R. D. Kravolec, Journal of theAssociation of Official Agricultural Chemists, No. 3, vol. 36, August 15, 1953, P. 907.

The following example shows the preparationof a ureaformaldehyde condensation product containing complete fertilizer where ammonia alone served to provide V.proper pH adjustment.

EXAMPLEzI The following ingredients were tumbled in a conventional rotary mixer, the urea being admixed to the=super phosphate'in advance. AFormaldehyde andanhydrous ammonia were sprayed in simultaneously.

In the above information at a ureaeformaldehyde :mol ratio of :1 there was no pH adjustmentotherthan .that obtained by the anhydrous ammonia. Since the '.pH

as made was 4.1, an immediate `cooling kwas necessary Yto a low temperature of about 75 F. The resulting WIN after a two-week cure was 3.9.and the A.IIfwas-42. The urea served to supply 4.88 units of nitrogento=theproduct (98.75 lbs.) and the percent urea 'Ncondensed to yWIN was 80.

VIt is vmost important to carefully control the curing temperature after the first 24-hour period. Ordinarily, the temperature at which the initial condensation reaction takes place will be in the neighborhood of 160 F. or somewhat above since this is the temperature prevailing within a mixing chamber during an ammoniation reaction involving ammonia and a phosphate. As mentioned earlier, Vit is possible under certain extreme conditions of U/F mol ratio and pH to use 160 or slightly above as a curing temperature. However, this makes the production of a suitable product an extremely dificult proposition and accordingly it may be said that if, under ordinary circumstances, this temperature is allowed to exist for a substantial period of time (generally over about `24 hours depending on the U/ F ratio, temperature, and pH), following the initiation of the condensation reaction, a product is obtained which is unacceptable as "it will be over condensed and have a low nitrogen Aavailability index.

One possible way fof avoiding a Yhigh temperature throughout .the entirety of the condensation reactionfis to mix only a portion of the formaldehyde with urea, and subsequently, after cooling the substrate and'ureaformaldehyde mixture, add the additional formaldehyde and complete the reaction at the lower temperature. .This approach achieves proper results since a convenient way to .lower the temperature of the substrate and reacting ingredients is simply to rehandle them. Rerun- Vning the fertilizer mixture through the mixing drum at the timeof the addition of the extraformaldehydenecessarily causes cooling. For example in one such.test,.the temperature just prior to the remixing operation .was about F. and was easily lowered to about 100 F. by the rehandling and remixing. Consequently, the temperature prevailing during the extended time period following contac-t of all the urea with the entire '.batch of formaldehyde was maintained at a relatively ,low level.

'If all of the formaldehyde had been added to thefurea initially, and the high emergence vtemperature had Vremained unbroken for a substantial time, the Waterlinsoluble nitrogen bound up with the 'urea-formaldehyde `condensation product would have ultimately displayed low agronomie activity. The amount of hot Water-insoluble nitrogen would have increased and the available insoluble nitrogen would have decreased. The high temperature prevailing subsequent to the first mix then was necessarily broken before ,the remaining-portions of the formaldehyde charge were introduced.

or, higher, oras.low as 1.7:1 or lower.

EXAMPLEVII lst'Mixz j 5 Lbs./ton .Y Single'superphosphate 1,050 Y Sulphate of potash 157 Anhydrous ammonia 31 Urea 206 I `Liquid formaldehyde (377% by Aweight of 4CH2O) 120 Dolomite U 4 Y 460 i Nel'^(minor` element base) 20 2nd Mix: Liquidformaldehyde'37% 85 ,Dye^"' 0.5

The U/F mol ratio in the first mix is equal to 234:1. 'I`he1irst`iriix wascured 24 hours at 125 F. In the second stage the remainder of theformaldehyde was a'dded resulting in an over-all U/F mol ratio 'of 134:1. The mix was then cooled to 80 F. The WIN was equal to 2.50'a't 50 A.I. .In the above formulation the temperatures of cure are necessarily lower than where additional pH adjustment occurs'when using additional lime or other basic material.Y The U/F mol ratio in the first proper` holding temperature, in 'this case' .100".` 'The table whichappears below, Table 2, shows' results of Vthese tests'wherein the maximum time at 140 5F; is shown inthe left-hand column andthe availability index of the condensation product obtained appears in the second column beneath veach of the U/F ratios.v The total curingV time was, in each ease, two weeks with km'ostrof the cure being effected at 100 F. The test results set out in Table 3 alsojshow clearly that the A.I. decreases constantly even where more moderate cure temperatures (120 and 1 15 F.) are selected, thus further pointing up the criticality of the cure temperature.

In the t'wo tables immediately following and in others which appear later the heading Percent Cond, refers to the percentage of the urea nitrogen which condensed to w aterinsolublenitrogen, based upon .the quantity of Vurea nitrogen present initially.. In each case,"urea was usedto supply a given quantity of nitgrogen, 4.16 units inthe tests of Table Y2 and 4.88 units in the tests of Table 3. Theheadings WIN refer to units of nitrogen condensed to water-insoluble nitrogen. Accordingly, Percent Cond. is secured by dividing WIN by 4.16 in Table 2 and by 4.88 in Table 3,.and multiplying the quotient by 100.

Table 2 U/r'=1.6 U/F=1.7 U/r-Ls Hours at Y Y 140 F Per- Per- Per- WIN 5.1. cant WIN AJ. cent WIN .4.1. cent Cond. Cond. Cond.

2.25 5s 54 1. so 62 43 1.55 76 37 2. 5s 6o 2.25 54 54 2.16 63 51 2.75 53 56 2. 45 55 59 2. 25 57 54 V2. 4s 65 2. 46 55 5s 2.25 52 54 2. 8 5 3s 6s 2. 65 ,4e 64 2. 3o 51 55 2. 9o 34 59 2. 65 45 64 2. 55 48 61 2. 29 68 2. 30 35 67 2. 55 50 61 pH (as made) 5. 70 5. 70 5. 70

i Y 37% formalin used. mix may vary considerably. It may be as highas 6.7:1 Table'3 This twolstage approach is merely one. convenient method of insuring that a high temperature will not obtain for too long a period of time with all of the formaldehyde being in contact with. the urea. The preferred Yapproach as shown in the example is to mix all of the formaldehyde with the urea Aat once and carefully control the temperature so that the high mix temperature does not last for more than a few hours and at the most 24 hours. All of theV formaldehyde may be added to all lof the urea at therr'st stage and removed from the mixer immediately, or set aside for several hours or a day at the most, and then run'through the rotory mixer a second time or otherwise cooled. The cool air passing through the interior of the mixeriduring the second handling causes a temperature drop to a level which does not Vinduce the formation of the over condensed urea-formaldehyde product. Preferably, the temperature of the mix followingtbis second mixing operation should be in fthe`neighborhood of about 'P'. to about 140 F.

depending lon the U/F ratio Vand pH. The pile is then set aside and allowed to cure for a Vperiod of about 2 `weeks and may be then sold as the A.I. and condensa- Ytion level are relatively stable by this time.

To more clearly point up the danger of allowing high `cure'temperatures to prevail even for a relatively short period of time (24-48 hours) a series of tests were Vrun Ywherein U/ F-condensation products were prepared under Yconditions such that the products would be expected to EFFECT OF TIME CURE AT VARIOUS TEIVIPERATURES USING 37% FORMALIN Note that Where,V in theV results set out in Table 2, a period of about'2 days Was allowed to elapse at a cure temperature of Vthe availability index of the ultimate product dropped significantly. In the case of .a U/P` product having a ratio of urea to formaldehyde of 1.6 to 1 the drop was `from 58 to 29, for .example v ,Availability -index drops in the'vicinityrof about 20-30 .points were obtainedY in each of the other tests. e Under most conditions, Va drop of this magnitudewould render .the'U/ F condensate unacceptable.V Y Accordingly, the 24 -hour maximum `holding period at theV temperature of manufacture (or at any temperature significantly above vthat shown as appropriate on the graph, for that matter) while not an absolute' minimum, Vparticularly at high U/P` ratios, has been selected to afforda margin of safety. 'As shown in the first test reported in Table 2, 24 hours at 140"Y where the U/F ratio is` 1.6 tol is anfabsolute maximum but, as can be seen from the other tests reported there, it becomes less critical'where'highe'r U/F ratios are selected.

While it is `commoiifor the availabilityrindex `tofdrop iTdb'lei; off to a certainiextent duringtthe .twoweekrurrng'perroi .TWO WEEKS -CUREAT 755K nevertheless, Vthe Adrop where .the proper .holding temy perature obtains .is by no rmeans kas .significant as thatob- [6-10'4 grade using 37%f0m1ml tained in the above tests. fIn the tests reported above .in Table 3, products were manufactured'which .might be Zweeks expected to be Within :the vscope of .this invention .and Formula Ulli-M01 13HV (as -PH (2 No. Ratio made) wks.) l the curing temperatures in each case were Within the -WI-N A1, 'percent limits set forth in the graph. Note .that in the rst test Cond. -wherein the U/F ratio was 11.5 to '1,the drop in avail- 10 1 2 7 3 8 5 40 6 3 95 i 04..... 1.00 0 5 -i. -abilityiudex obtained was only -from 57 to 53 over four 105m 1.00 .3.20 3 92 4 00 .34.2 77 days and only to 49 over 11G-days. In a further series i. 00 3.85 4l1.20 4.63 32.2 l1 00 of tests, the U/.P` ratio selected was 1;6 Vto 1 and the jgg g .g (11g I-S? `v3(1) cure temperature '115 the Al. drop over 4 days was 1.00 A4. 52 A4. 40 4.00 53.3 95 only from 67 to 60 and over 14 days .to 58. Thus, in jgg g 3:22 ggg .2g each case, where a curing temperature within the desired 1.25 3.95 3. s0 3. 75 `03 v '73 range was used the drop'was much less than thatwob- (25g 'jg jg fg 2:2 gg tained Where curing temperatures.of140 were used -ini- `gg y50 ilig gg g3 tially-even though vthe product was vcooled thereafter. .zfno 3.22 3fm 85 `37f7 55 it is seen, therefore, that even V.arelatively limited period gg g3 gg g2 gg Vof time at a high cure `temperatureca'n adversely Aaffect 2:00 3:90 3EME 1 '25 5:2 25 the product, 'especially where `relatively low VU/F 'mol gto) 3(8) ggg ig ggg gg ratios and pHs are'selected. 213g 3:17v "3j 51' `173 i310 33 To show the variation in conditions and urea-to- 511g. ggg' is.; formaldehyde mol ratios which Vcould "be'selected using 2:75' *'32'10' `31'60' 11'75' :43f2 '32 a basic formula ;(given in Example'I) and stillrsecure gg ggg .t-gg. a urea-formaldehyde 'condensation product 'having the 2.75 3.50 .3.75 .1-00 52.7 .21 proper availabilityindex and ;sulicien'tly high degree of condensation, a large number of additional tests Were-run varying the pHs, curing .temperatures and .urea-toformaldehyde mol. ratios.

For `each cure temperature listed the `analytical vre- Table 5 sults for water-insoluble nitrogen '(-W.I.N,) landfavaily o .ability index (Al.) are arranged 'with respect to in- 35 TWO WEEKSCURE T100 TF' creasing U/F mol 'ratio (between 1 and :2.75 to.1`),'and [5-10-4 gradeusing 37%fformaiin] with respect to increasing'pH (as made). As can be seen, within each U/F` mol ratio grouping, 'the A;I. in- Femm U/F M01 p Y WIN A I Percent creases with an increasingpH The data obtainedfrom Ratio (as made) (2 Wks) Cond. these tests was suflicient to indicate the -properU/Fmol l 1.00 5. si .5..00 :.35904 35 93 ratio, pli and cure temperature to obtain a product hav 1.00. .5 45 .5.23. .37.68. 40. 5 88 ing a minimum A.I. of 40 and a .condensation of at img' 5:43' sei' 3:10 "61.2 73 least From the .data here, the graph was pre- 1125 jgo jg gjfgg ."gjg 2(5) pared. The isotherms bearing cure temperatures repreg5 ggg g sent the maximum temperature at any given pH or'U/F Y2100Y Y4200A A3%77 A20a ui855' Ai3 '2 n Y niol ratio which would be expected to l.yield .a'product 'j ggg 51; naving the desired 40 A1. Since an increase in pH ggg fg egg.; :gli or U/F mol ratio, 'Where the temperature Ais held conjg 'gg 0 if? 53 5 5. 25 stant, assures va higher A.I. than that which has been 72.75 4:28p 744:02 1:00 89:0 21 set as a minimum, it may be stated that the area to the right of and above any given isotherm contains the U/F mol ratios and pHs (at the time of manufacture) which for the temperature selected will assure a prod- V uct having better than a 40 A.I. level. In other words, Table 6 to use the graph all one need do is select a cure1temo perature represented by any one of the isotherms. He TWO WEEKS CURE AT 125 F may then conclude that any point in the area above and i5-1H grade using 37%.forma1in1 to the right of that temperature curve represents a pH and U/l T mol ratio relationship which will yield a prod- Formula Uv/F M01 WIN Al Percent uct having better than a 40 A.I., provided of course, N0. .Ratio (as made) (2 Wks) Cond. that the cure temperature is held at this level or below. Of course, if the point is directly on the curve itself, gg g'g "i s? the A I. will be about 40. It will be noted that the cur- 'i 00 ei5 `@i541 260 5417 02 ing time selected in each of the tests listed below was "i183 ggg gl 3(5)'A ig two weeks. It was felt most practical to base Vthe direc- {1-160 4-92 -4--28' 882 i5-i7 .68 1.60 5.17 .4.50.y 2.00 V44.54 -69 tions for securing a product of this invention .upon this 2.00 4.15 3.93; .2.35. 29.7 53 v2.00 4.40 Y .4.09v .2.45 '34,;5 54 time period because two weeks is a fair average of the 2200 4.40 Y 4 7207 2.1501 .43.2, 53 time lapse between the manufacture and bagging and 2.23 gg LL-g- 3.48` 52-3 59 shipping fertilizer. The columns labeled pH (as^made') 2140 4:30' 10 2j gj' Vcontain the various pHs observed within 2 zto 4 minzg if?? 97) utes after all ingredients were charged -into the reaction r:2l-15 4123 945.15; 175 i215 a6 vessel.

TabIe''7 -TWO WEEKS CURE .ALT 140.F.

[6-10-4 grade using 37% formalin] fagassgsso Formula U/F Mol pH pH WIN A.I. Percent No. Ratio (as made) (2 Wks Cond.

Table 8 TWO WEEKS CURE AT 160 F.

[6-10-4 grade using 37% formalin] Formula U/F Mol pH pH WIN .4.1. Percent No. Ratto (as made) (2 wks Cond. Y

1. 90 6. 60 7. 00 2. 28 38. 7 55 2. 05 6. 50 6. 72 2. 35 33. 0 56 2. 6. 50 6. 90 2.05 50. 2 49 2. 6. 48 7. 00 2.00 44.3 48 2. 50 6.00 6. 68 2.03 41. 0 48 2. 50 6.25 6. 80 1. 90 48. 8 45 2. 75 5. 10 'f' '5l 85 1. 75 30. 7 42 2. 75 5. 42 5. 95 1. 70 34. 2 41 2. 75 5. 65 6. 30 1. 68 36.0 40 2. 75 5. 83 Y 6. 05 1. 70 44. 7 40 2. 75 5. 97 5. 68 1. 75 45. 0 42 2. 75 6. 40 6. 80 1. 70 46. 3 41 2. 75 6. 53 7. 10 1.98 51. 5 47 Table 9 TWO WEEKS CURE AT VARIOUS TEMPERATURES [6-10-4 grade using 37% formalin] Formula U/F pH p Cure VPer- N o. Mol (as (2 wks WIN A .L Temp., cent Ratio made) F. Cond.

Table 10 TWO WEEK CURE AT VARIOUS TEMPERATURES ON USING OTHER THAN 37% FORMALIN the`ureatdformaldehyde mol ratios, the family of curves .(one curve representing each temperature) shown in the graph is Obtained. This graph shows. all of the important manufacturing conditions for securing a product having the desired minimum availability index. At a cure temperature of 164 there is virtually only one set of conditions which is of any importance in manufacturing a proper U/F` product; a U/F mol ratio of 2.75 to 1 and a pH of 6.5. With decreasing cure temperatures the usable conditions increase in number until, at the lowermost practical cure temperature, 75 F., the entire area bounded by A,B,C,D designates U/F mol ratio-pH interrelationships which yield the desired product; one having at least a A.I. The various limits have been chosen for the following reasons:

The lowermost urea-to-formaldehyde ratioV (1.0 to 1.0) was chosen since the cost of formaldehyde is high relative to the other ingredients. It would be uneconomical to produce the U/l;` material for use in a fertilizer at U/F mol ratios much below 1.0 to 1.0 as long as the U/F material secured at higher ratios is Vagronomically satisfactory. Also,'in the U/F mol ratio range of between .5 and 1.0 to 1.0, the 40 A.I temperature line rises very sharply and the additional larea obtained representing usable conditions is quite'small-leaving little leeway in pH above the selected temperature line.

The upper urea-to-formaldehyde mol ratio (2.75 to 1) was selected since at this point the .percentage of the urea converted to water-insoluble nitrogen ranges generally much lower than the preferred.

'The uppermost pH limit (6.5) was selected because, as pointed out earlier, the U/F condensates of this invention are most economically Ymade in situ with phosphatic fertilizers and preferably at the time of the ammoniation of superphosphates. When the pH of a superphosphate isl raised too high, reversion of various ingredients of the super to unavailable forms is encountered-representing a loss.

'Ihe lowerrnost curing temperature (75 E), was selected because it is neither practical nor economical to cool much below this temperature. Also, a condensate formed at such a low temperature might thereafter be Vstored at a higher temperature, for example 90 F., for an extended time after being sold and this would cause further condensation .ofthe original product, thus lowering its availability index. Even where atemperature of F. is used, the product is not as stable as one prepared where a higher curing temperature is employed and, accordingly'75 F. is by no means the most desirable temperature for commercial use. Urea-formalde- VARIOUS GRADES Formula Ulli` Cure No. Grade CHO Source Mol pH WIN AJ. Temp.,

. Ratio F.'

U/F Solution 1. 6 5.85 4. 60 45 125 U/F Solution plus 1. 5 5. 50 4. 75. 40 86 Para ormaldehyde. Y U/r` Solution..-" 1. 6 5.70 5.10 40 125 --do 1.8 5.70 v4.50 as 14o do 1. 6 5.40 2.50 44 125 U/F Solution plus 1. 4 .5. 00 70 49 120 Paraformaldehyde. u 12-12--12v Hexamethyleue 1.6 4.10 5. 45" 47 86 tetramina. 12-12-12 1. 6 4. 1o e. 25 37 10o 12-12-12 1.6 41o o. 25 31 120 12-12-12 1.4 4.40 .7. 95 4o 10o 12-12-12 1. o 4. o3 6. o5 40 115 12-12-12 1. e 4. 20 3. 3o 43 8o 12-12-12 1. 6 5. 75 5. so 42 125 When material taken from Tables 4-8 and 10 above hyde products formed at the highertemperatures, cured showing a -product having about a 40 A.I. level 1s plotted for from l to 3 weeks and thereafter cooled are relative- -with the ordinate carrying Ithe pH values and the abseissa ly stable. For example, urea-formaldehyde materials cured at 100 F. to 125 F. for two weeks showed'only abouta24A;I. drop; after six monthsat 70 F; to 85 F. storage;V

A. reading. of the graph therefore. indicates that the U/F` mol ratios yand pHs (asV made) are limited and defined by the cure temperature used or encountered. For example, where a` cureV temperature of 164 F. is used, pH must be about 6.5 andthe urea-to-formaldehyde mol ratio about 2.75. Where a cure temperature of 1760" F. is used, all pHs and U/F mol ratio combinations bounded.' by the pH line of 6.5, the U/F mol ratio lines of 2.25 and 2.75 and the 40 A.I.-160 F. line may beemployed. Where a cure temperature of 150 F. is selected,.one may usev all pHs and U/F mol ratios bounded by the pH line of 6.5, the U/F mol ratio lines' of 1.95 and 2.75 and the 40 A.I.-150 F. line. Where a cure .temperature of 140 F. is selected, all pH and U/F mol. ratio combinations bounded by the line pH 6.5, the U/F mol ratio f lines 1.58 and 2.754 and the 140-40 A.I.. line are acceptable. For a cure temperature of 125 F. these conditions become the pH and U/F molratio combinations bounded by the pH line of 6.5, the U/F mol ratio lines of 2.75 and 1.0 and thev 125 o`40 A.I. line. In the case of 100 F. as a curing temperature, the pH and U/F mol ratio combinations fall within the pH line of 6.5, the U/F mol ratio lines of 1.0 and 2.75 and the-40 A.I.100 F. line. Finally, in the case of a cure temperature of 75, the conditions are all pH and U/F mol' ratios bounded by the pH line of 6;5, the U/F mol ratio lines of 1.0 and 2.75 and the 40'A.I-75 F. line. Obviously, for Vany other temperature which one might select it is possible using inormationpresently in .the graph t'o draw an addition to the family of curves given. Thenew line would represent a new temperature and be properly spaced from the lines on either side of it, depending on the proximity of the temperature selected to that` representedY by any of the lines already plotted. Given this new temperature line, one may read directly from the graph the conditions which must be maintainedV if a product of at least 40 A.I. is to be obtained.

The 40 A I lines given for each cure temperature, of

course, represent the minimum conditions of pHv andV U/I-` mol ratio which one might possibly use and still obtain the desired 40 A I. product for the water-insoluble nitrogen portion of the U/F material. As a practical matter, however, it is most desired that the pH used be about 1 point above the 40 A I. temperaturev line for a U/F mol ratio ranging from 1.0 up to about 2.75. This insures a higher than 40 Al., usually in .the range 50 to 60.

Generally, it may be stated by Way of. simplification that from the standpoint of the products A I. the preferred conditions at a given temperature fall to the right of and below the lines EF and FG respectively, the temperature used being to 40 degrees below the maximum which the graph would indicate as permissible, the pH being below 5.5 and the mol ratio being 1.4 to 1 or greater. Another consideration in delimiting. the preferred area on the larger graph is the percentage of condensation of the total urea nitrogen to water-insoluble nitrogen. As long as one selects conditions to the left of and above the lines GH and HE respectively, it. may be predicted with reasonable certainty that the condensation product secured will. be at least 50% condensed. Referring to tables 4-8`it will be seen that:

At a. 75 F. cure, a mol ratio of 2. and a pH of 3.2, the percent urea nitrogen condensed is 55;

At 100 F. cure, a ratio of 2. and a pH of 3.72, the percent urea nitrogen condensed is 49;

At 125 F., a ratio of 2. and a pH of 4.75, the percent urea nitrogen condensed is 50; and

At 140 F., -a ratio of 2.4 and a pH of 4.75, the percent urea nitrogen condensed is 51.

Therefore the parallelogramv EFGH provides a safe marginboth with respect to availability index ofthenitrogen` in the condensationv product and thel percentage of urea nitrogen condensed to. water-insoluble nitrogen. The' one will be in excess. of 40 (Al.) andthe other in excess ofV 50 (percent Cond). ThusV it is preferred to use a U/F ratio rangingbetween 1.4 and 2.0 to 1.0 (and rnostf preferably a pHv aboutv 1. above. the minimum pH usable for any given temperature to provide an extra margin of safety), such temperature preferably ranging between F. and 115 F. The 75 F. minimum is selected in part lbecause lower temperatures necessitate the useof refrigeration equipment for curing throughout a fair portion of the year. Accordingly, from the standpoint of ease of operation,` a practical minimum curing. temperature of F. is recommended. Most preferred is pH 5.0 immediately following making, a U/F ratio of 1.6 to 1.0 and a storage cure temperature of about F. forv at least one week and preferablyv two;-

TheV improved results reflected in increased A I. levels due. to decreased curing temperatures can be seen in Table 9 wherein data is set forth showing results of curing two types of U/F products (different U/F ratios) at.varying temperatures. Note the decrease in A.I. obtainedv yas cure temperatures were increased.

An improved product of the type set forth in the aforementionedy application toMortenson et al. covering Non- Burning Plant Food may be prepared by carefully governing the manner in which the pH of the acidic phosphate substrate (generally and preferably a superphosphate) is raised to theV proper level as' shown in Example IH. If such non-burning plant foods are to be prepared using ammoniatedy superphosphate and charging the urea and formaldehydev directly into the container in which the ammoniation reaction is taking place,- the pH necessary tov secure the proper condensation and A.I. in the urea-formaldehyde product may be rather high. -As

vpointed out in the aforesaid Mortenson and Kealy application, thequantity of the ammonia allowed to contact superphosphates must be kept at a relatively low level if the production of salts which burn green leafy plants is.to be avoided. AtV most, the ammonia must be reacted only stoichiometrically with the free phosphoric acid and monocalcium phosphate in superphosphate to convert theseto monoammonium phosphate and dicalcium phosphate.. If this ammoniation reaction is' not terminated at precisely' this` point (or before), ammonium sulfate or. diannnonium phosphate, both of which burn green leafy plants, will' be formed. Accordingly, beyond this point ammonia, the customary material used to raise the pH, mustl be no longer utilized and another non-ammoniacal soluble base preferably a material such asV calcium hydroxide (hydratedlime) calcined dolomite or magnesium oxidei must; bev used in its place. In other words, any materiali that is` nontoxic to plants may be used to raise the pH (other than an ammoniacall material) providedthat the base selectedfdoes not react with any of the other ingredients. present inthe mix to form a burning compound. Reference to the tables in the Mortenson et al. application indicates whichsalts may be formedwithout encountering a product which tends to cause plasmolysis.

EXAMPLE HI Results of a run usingan appropriate set of conditions for a product havingV a urea-to-ormaldehyde ratio of l.53:1` and a pH at the time ofmanufacture of 4.85 where the extended curing temperature was reduced to about 100 F. (time of cure 14 days) follow. The product was cooled immediately after mixing. The water insoluble nitrogen level (WIN) was 2.67 and the availability index 57.3. The percent of urea nitrogen which was WINV (that percent condensed) was 64.5 percent and the urea was used to supply 4.15 units of nitrogen.

-mxer within a period of no more than 24 hours.

The various ingredients were mixed in the fashion of those of Example I. i

The invention also contemplates the use of any suitablephosphatic substrate including various mono and di phosphates and meta phosphates. Preferably the ureaformaldehyde condensation product is prepared at the time when the ammoniation of a normal or triple superphosphate is taking place. This provides an easy method for raising thepH to an acceptable levelA (due to the presence ofexcess ammonia).Y If ammonia alone is used to raise theY pH to a relatively high level, any hope of securing a product which, as defined bythe aforementioned application of Mortenson and Kealy, is non-burning, must be dispensedwith Large quantities of ammonia neces' sarily result 1n the production of salts which burn green leafy plants. However, if a non-burning product is desired and if all of the ingredients are selected from those recommended in the Mortenson and'Kealy application, theobtaining of such a product may be assured by terrnlnating the ammoniation of the superphosphate at the stolchiometric level previously described. YBeyond this point, non-ammoniacal base materials of the type de` scribed should be employed to raise the pH to a higher level. The temperature desired may be obtained through any one of several methods. Most conveniently, the product may be manufactured with all of the urea being contacted with all of the formaldehyde at one point and the mix, afterY being removed from the mixing chamber, having its temperature broken in any convenient fashion such as by immediate cooling or by a rerun through the Sufficient fresh air is ushed through so as to cause the mixture temperature to drop `substantially below the initial reaction temperature. As a further safeguard, the addition of a portion of the formaldehyde to the ureaV may be held olf until the second mixing step. This will insure that over condensation does not take place simply because the necessary formaldehyde is not present at the time when high temperatures prevail.

It will be remembered that it was pointed out above that any given Vminimum curing temperature may be exceeded for a short period of time, about 24 hours on the average, without adversely affecting the product to too great a degree. Accordingly, where the appended claims refer to curing (for one week) at a temperature no greater than a given minimum, it is not intended to exclude from their coverage such short time, high temperature treatment. All that is required under ordinary conditions is that the excessive temperatures not beallowed to prevailV for longer than about 24 hours in orderY to yield the desired product.

Also, the claims refer to curing periods of one week. As pointed out earlier, curing times ordinarily range between one and three weeks. However, after about one I claim:

1. A process for the manufacture of a urea-formaldehyde condensation'product in the presence of a substantially dry fertilizer solids substrate which comprises: contacting said urea and said formaldehyde in the presence of said fertilizer solids substrate at a pH of between about 4.15 and 5, said urea and said formaldehyde being present in mol ratios of between' about 1.7 and 6.7 mols urea to 1 mol formaldehyde; cooling the mixture so formed within about 24 hours to a temperature less than about 100 F. and contacting said mixture with su'icient additional formaldehyde to adjust the urea to formaldehyde mol ratio to between about 1 .0 and 2.75 mols urea to l mol formaldehyde; and allowing said mixture to cure whereby to produce a mixed chemicalV fertilizer having a ureaformaldehyde condensation product as a source of waterinsolublenitrogen, said urea-formaldehyde product having a water-insoluble nitrogen availability index of at least about 40. j

2. A process for the manufacture of a urea-formaldehyde condensation product in the presence of a substantially dry fert'dizer solids substrate which comprises: contacting said ureaand said formaldehyde in the presence of said fertilizer solids substrate at a pHof between about 3.5 and 6.5, said urea and said formaldehyde being present in mol ratios of between about 1.7 and 6.7 mols urea to 1 mol formaldehyde; cooling the mixture so formed to a temperature less than about 160 F.; contacting said mixture with suiicient additional formaldehyde to adjust the urea to formaldehyde mol ratio to between about 1.0 and 2.75 mols urea to 1 mol formaldehyde; and a1- lowing said mixture to cure whereby to produce a mixed chemical fertilizer having a urea-formaldehyde condensation product as a source of water-insoluble nitrogen, said urea-,formaldehyde product having a water-insoluble nitrogen availability index of at least about 40.

3. A process-for the manufacture of a urea-formaldehyde condensation product in the presence of a'substan- -tially dry solid phosphatic' fertilizer substrate which comprises: reacting urea and formaldehyde in the presence of said phosphatic substrate at a pH of betweenl about 3.0 and 6.5, said urea and formaldehyde being present in mol'ratios of between about 1.0 and 2.75 to 1f;V before about 24 hours thereafter adjustingV the temperature of the mixture so formed to between about F. and 164 F.; and allowing said mixture at said temperature to cure, whereby to produceV a substantially.dryimixedrchemical fertilizer having a urea-formaldehyde condensation prod,- uct as a source of water-insoluble nitrogen, said urea- .formaldehyde product having a water insoluble nitrogen availability index of at least about 40.

4. In a process wherein a substantially dry superphosphate material is ammoniated and simultaneously therewith urea and formaldehyde are contacted to form a substantially dry fertilizer mixture containing a urea-,formaldehyde condensation product, the improvementvwhich comprises: adding sufficient ammoniacal material to said superphosphate to satisfy the stoichiometric requirements for just converting the free phosphoric acid V.and monocalcium phosphate of said superphosphate'to monoam- -monium phosphate and dicalcium phosphate; adjusting, the pH yof said superphosphate material to within the range of about 3.0 to 6.5 by theaddition theretofof an inorganic, non-ammoniacal soluble basethat is nontoxic to plants and that will not react with vany oftheother ingredients present in themixture to form a burning compound; reacting said urea and formaldehyde in mol ratios of betweenabout 1.0 and 2.75 to 1; before about 24 hours thereafter adjusting the temperature of the mixture so formed Vto between about 75 F. and .160 F. and allowing said fertilizer mixture at said temperature to cure whereby to produce a lsubstantially dry mixed chemical fertilizer having non-burning propertiesand having a urea-formaldehyde condensation.productrgtheren as a source of Water-insoluble nitrogen, said urea-formaldehyde condensation product displaying a water-insoluble nitrogen availability index of at least about 40.

5. In a process wherein a substantially dry superphosphate material is ammoniated and simultaneously therewith urea and formaldehyde are contacted to form a substantially dry fertilizer mixture containing a urea-formaldehyde condensation product, the improvement which comprises: adding suflicient ammoniacal material to said superphosphate to satisfy the stoichiometric requirements for just converting the free phosphoric acid and monocalcium phosphate of said superphosphate to monoammonium phosphate and dcalcium phosphate; adjusting the pH of said superphosphate material to within the range of about 3.2 to 5.5 by the addition thereto of an inorganic non-ammoniacal soluble base tha-t is nontoxic to plants and that will not react with any of the other ingedients present in the mixture to form a burning compound; reacting said urea and formaldehyde in mol ratios of between about 1.4 and 2.0 to 1; before yabout 24 hours thereafter adjusting the temperature of the mixture so formed to between about 75 and 140 F. and allowing said fertilizer mixture at said temperature to cure Whereby to produce a substantially dry mixed chemical fertilizer having non-burning properties and having a ureaformaldehyde condensation product therein as a source of water-insoluble nitrogen, said urea-formaldehyde condensation product displaying a Water-insoluble nitrogen availability index of at least about 40.

6. A method of compounding a urea-formaldehyde condensation product for use in substantially dry mixed fertilizers in the presence of a substantially diy solid phosphatic substrate wherein the Availability Index of said urea-formaldehyde condensation product at least about 40, comprising: selecting a product curing temperature from the family of curves of the gure; reacting urea with formaldehyde in the presence of said solid phosphatic substrate; adjusting the pH and the mol ratio of urea to formaldehyde so as to be represented by a point Within the area to the right of and above the line representing the curing temperature selected and the area A B C D of said figure; and thereafter curing Ilthe product so formed for at least about one week at no greater than said selected curing temperature.

7. The method of claim 3 wherein the said condensa'- tion product is :formed in the presence of a superphosphate substrate undergoing ammoniation.

8. A method for compounding a urea-formaldehyde condensation product for use in substantially dry mixed fertilizers, said product having an Availability Index of at least about 40 comprising: reacting in the presence of a substantially dry solid phosphatic fertilizer substrate urea with formaldehyde in a mol ratio of 1.6 to 1.0; adjusting the [pI-I to about 5.0; and thereafter curing the product so formed for a period of at least about one Week at a temperature at least about F. and not in excess of about F.

9. The method of claim 8 wherein the said condensation product is formed in the presence of a superphosphate substrate undergoing ammoniation.

10. In the manufacture of a substantially dry mixed fertilizer, the steps comprising forming a tumbling bed of substantially dry phosphatic fertilizer solids, contacting said solids with urea, formaldehyde, and an ammoniacal material, in proportions such that the ratio of urea to formaldehyde will be between about 1.0 to 1 and 2.75 to 1 and the pH `of the resilient mixture will be within the range of 3.0 to 6.5 whereby the phosphatic solids will be ammoniated and a urea-formaldehyde condensation reaction will be initiated on the substrate `of solid fertilizer ingredients, adjusting the temperature to between about 75 and 164 F. and correlating the temperature in said tumbling bed of solids with the urea to formaldehyde ratio and the pH of the mixture to avoid immediate completion of the condensation reaction, and thereafter allowing said condensation reaction to go to completion whereby the condensation product so formed has a nitrogen availability index of at least about 40.

References Cited in the ile of this patent UNITED STATES PATENTS 1,953,419 MacIntire Apr. 3, 1934 2,766,283 Darden Oct. 9, 1946 2,618,546 Davenport Nov. 18, 1952 2,827,368 Mortenson Mar. 18, 1958 UNITED STATES PATENT oEEIcE CERTIFICATE 0F CORRECTION Patent No, 2,955,930 October ll, 1960 Column 5, line ll, for "adn" read and line '59, for "NHSH" read NHSN column 6,. line 9, in the tableY first line thereof, for "(single" read (single) Y same column 6? line 13, in the table, fifth line thereof, for` Uefa read Urea column l0, Table 5l sixth column last lineA thereof,v for 89O" read 59C --g column 18, line 23, for

Signed and sealed this 4th day of April 1961.,

(SEAL) Attest: ERNEST W. SWIDER KINK ARTHUR w. CEOCKER Attesting Officer Acting Commissioner of Patents 

1. A PROCESS FOR THE MANUFACTURE OF A UREA-FORMALDEHYDE CONDENSATION PRODUCT IN THE PRESENCE OF A SUBSTANTIALLY DRY FERTILIZER SOLIDS SUBSTRATE WHICH COMPRISES: CONTACTING SAID UREA AND SAID FORMALDEHYDE IN THE PRESENCE OF SAID FERTILIZER SOLIDS SUBSTRATE AT A PH OF BETWEEN ABOUT 4.15 AND 5, SAID UREA AND SAID FORMALDEHYDE BEING PRESENT IN MOL RATIOS OF BETWEEN ABOUT 1.7 AND 6.7 MOLS UREA TO 1 MOL FORMALDEHYDE, COOLING THE MIXTURE SO FORMED WITHIN ABOUT 24 HOURS TO A TEMPERATURE LESS THAN ABOUT 100*F. AND CONTACTING SAID MIXTURE WITH SUFFICIENT ADDITIONAL FORMALDEHYDE TO ADJUST THE UREA TO FORMALDEHYDE MOL RATIO TO BETWEEN ABOUT 1.0 AND 2.75 MOLS UREA TO 1 MOL FORMALDEHYDE, AND ALLOWING SAID MIXTURE TO CURE WHEREBY TO PRODUCE A MIXED CHEMICAL FERTILIZER HAVING A UREAFORMALDEHYDE CONDENSATION PRODUCT AS A SOURCE OF WATERINSOLUBLE NITROGEN, SAID UREA-FORMALDEHYDE PRODUCT HAVING A WATER-INSOLUBLE NITROGEN AVAILABILITY INDEX OF AT LEAST ABOUT
 40. 